Gaseous electric discharge device



GASEOUS ELECTRIC DISCHARGEDEVICE Filed July 17, 1956 Amen 70m:

l'aumfo 6: [701M510 AT ORNEY Patented Mar. 30, 1931 PATENT OFFICE2,075,641 GASEQUS ELECTRIC DISCHARGE DEVICE Eduard G. Dorgelo,Eindhoven, Netherlands, assignor to General Electric Company,a'corporationot New York Application July 17, 1936, Serial No. 91,195

In Germany July 8, 1935 1 Claim.

The present invention relates to gaseous electric discharge devicesgenerally and more particularly the invention relates to such deviceshaving a tubular container and a gaseous atmosphere therein consistingof or comprisinga metal vapor.

In the operation of devices of this type deposits of condensed vaporfrequently accumulate in the regions of the container between eachelectrode and the end of the tube adjacent thereto since these parts ofthe container are heated less by the discharge than the parts of thecontainer surrounding the discharge path between the electrodes andconsequently are at a lower 15 temperature during the operation of thedevice. This disadvantage is very noticeablein devices having a quantityof dimcultly vaporizable metal therein, that is a metal the vaporpressure of which is less than 1 mm. at a temperature of 200 0., such assodium, cadmium, magnesium,

for maximum efliciency; while the actual temperatures of their envelopeor bulb walls range from about 220 C. or less to about 275 C. or more.The boiling point of sodium being about 877 C., the sodium vapor in thecommercial lamp bulb is continually condensing on its inner surface andvaporizing again, with a tendency to accumulate and remain in any regionor area that is relatively cool, because of the slower vaporization fromthe cooler region. This means that the sodium vapor pressure in theenvelope will tend to fall below that corresponding to the general lamptemperature, and to approach that corresponding to the lowesttemperature envelope part which is detrimental to the light output andefiiciency of the device. When the structure of'the device is such thatparts of the con- 40 tainer are at a lower temperature than othercontainer parts during'the operation of the device increasing thetemperature of the whole container until the lowest temperaturecontainer part is at such temperature that an effective practicablesince the energy expended in heating the higher temperature parts-of thecontainer to a still higher temperature is wasted and further thecontainer may be weakened or strongly attacked by the metal vapor at thehigher temperature parts thereof.

The above disadvantage can be avoided by closing of! the part of thetube behind the electrodes from the other tube parts. This necessi- 55tates the mounting of a septum in the container zinc, or the like.Commercial sodium vapor lamps aim at operating temperatures around 250C.

vapor pressureis present in the device is imwhich increases themanufacturing cost oi the device. The problem can be solved by mountingthe electrodes close to the ends of the container whereat the currentleads are sealed.

. In this last structure the conducting seals are at an elevatedtemperature during the operation of the device and are apt to become gaspervious to terminate the useful life of the device.

The object of the present invention is to provide a gaseous electricdischarge device of the above type which is simple in structure, isinexpensively manufactured and which has a long operating life. Stillfurther objects and advantages attaching to the device and to its useand operation will be apparent to those skilled in .the art from thefollowing particular description.

xenon, is introduced into the lamp and is at a pressure of 2 mm. whencold, that is, at room temperature. During the operation of the de-'vice the metal vapor which penetrates into the space behind the maindischarge supporting electrode is ionized and the ionized vapor isattracted back to the cathode that is in the direction of the dischargepath between the main discharge supporting electrodes. The auxiliarydischarge thus creates a cataphoresis action which counteracts thediffusion of the vapor particles toward the cooler ends of thecontainer. The temperature of the seal at the end of the container canbe lower than that temperature at which the seal becomes gas perviouswithout causing deposits of condensed sodium to form on said seal parts.The pressure of the fixed gas in the container must be appreciable, thatis, 2 mm. or more, or else the cataphoresis action is not effectivesince the rate of diffusion of the metal is. too rapid at lower fixedgaspressure. In order to obtain a cataphoresis action sufiicient toovercome the difiusion of the vaporous particles into the cooler endportions of the container the discharge current of the auxiliary shouldbe at least 3% of the main discharge current. The auxiliary electrode isconnected to the current lead of the main electrode other than the mainelectrode to which said auxiliary electrode is adjacent by a resistancewhich regulates the auxiliary discharge current. This connection iseither in the container, external thereto but mounted thereon, or may beremote from the container.

In the drawing accompanying and forming part of this specification agaseous electric discharge lamp embodying the present invention and acircuit therefor is shown schematically.

Referring to the drawing the gaseous electric discharge lamp comprises aU-shaped container I having main discharge supporting electrodes 2 and 3sealed therein. Said electrodes 2 and 3 are electron. emitting whenheated-and consist of filaments of high melting point material, such astungsten, which are coiled helically and which are provided with anelectron emitting material, such as an alkaline earth oxide. The currentleads for said electrodes 2 and 3 are sealed into the pinch parts 4 and5, respectively of the container I. The external parts 6 and I of thecurrent leads of the electrode tube are connected to the secondary coil3 of the transformer 9, the primary coil ll of which is connected acrossthe terminal I9 and I! of the alternating." current source II. Theexternal parts I2 and I3 of the current leads for the electrode 3 areconnected to the-secondary coil I4 of the transformer IS the primarycoil I 6 of which is likewise connected toward the terminals I9 and I!of the alternating current source II. The electrode 2 is connected bylead Ii to the terminal I! of said current source II through theexternal resistance I8 and the electrode 3 is connected by current leadI2 to the terminal I8 of said source II. The electrodes 2 and 3 areheated to an electron emitting discharge supporting temperature by saidtransformers 9 and I5 respectively. When desired said electrodes 2 and 3are heated to this temperature by the discharge incident thereat inwhich case the transformers 9 and I5 are omitted, when desired.

10 Auxiliary electrodes 20 and 2I are mounted between said electrodes 2and 3 and the pinch parts 4 and 5 respectively of the container I. Saidelectrodes 20 and 2I consist of a cylindrical shell of high meltingpoint metal such as molyb- 45 denum, and are supported in said containerI by current leads fused into said pinch parts 4 and 5 respectively. Theauxiliary electrode 20 is connected through the resistance 22 to thecurrent lead I2 of the main electrode 3 and the auxiliary 50 electrode2I is connected through the resistance 23 to the current lead 6 of themain electrode 2. Said resistances 22 and 23 have a value of severalthousand ohms, when desired. The container I has therein a rare,starting gas, such as 55 neon, at a pressure of approximately 10 mm. atroom temperature and a quantity of dimcul'tly vaporizable material, suchas sodium, the vapor of which is light emitting during operation of thedevice. During the operation of the device 0 a positive column dischargeoccurs between the main electrodes 2 and 3 which act alternately ascathode and anode. Since the auxiliary electrode 20 is connected to themain electrode 3 through the resistance 22 a voltage diiierence existsbe- 5 tween "said electrodes and an auxiliary discharge takes placetherebetwecn, the electrode 20 serving only as anodefor said auxiliarydischarge. The electrodes 2 and 20 act asa single phase rectifier, adischarge occurring therebetwecn 7 only when the auxiliary electrode 20is positive .with respect to the main electrode 2. Secondly theauxiliary discharge current, which is, preferably, about 5% of themaindischarge current flows only in one direction, that is, in thedirection of the main discharge path between said electrodes 2 and 3.The auxiliary discharge between said electrodes 2 and 20 ionizes thesodium atoms which enter the space between said electrodes 2 and 20 fromthe part of the container I surrounding the main discharge path betweenthe electrodes 2 and 3. The sodium ions are attracted to the cathode ofthe auxiliary discharge, that is, to the main electrode 2, and thesodium vapor is thus prevented from reaching the pinch part 4. As theauxiliary discharge current flows only during that half cycle in whichthe auxiliary electrode 2 is negative with respect to the other mainelectrode 3 the cataphoresis action resulting from the. auxiliarydischarge opposes the cataphoresis action caused by the main discharge.The cataphoresis action caused by-the main discharge causes a movementof the sodium ion to the main electrode 2 when said electrode 2 isacting as a cathode. The advantageous eflect exerted by the auxiliarydischarge is enhanced by the relatively large gap between the auxiliaryelectrode and the main electrode which gap is greater than the diameterof the container I.

The auxiliary discharge between the main electrode 3 and the auxiliaryelectrode 2I has the same effect on the vapor ions and the sodium atomsare thus prevented from reaching the pinch part 5.

Gaseous electric discharge lamps having the structure described aboveare inexpensively manufactured, are eflicient in operation and have along operating life since the seal at the end thereof is at a lowertemperature than would be the case were the main electrodes 2 and 3mounted closely adjacent thereto and at the same time deposits ofcondensed sodium vapor are prevented from forming in the ends of thecontainer behind the main electrodes 2 and 3 and the sodium vapor isthus maintained in a vaporous condition in the main discharge pathbetween said electrodes 2 and 3 during the operation of the device.

While I have shown and described and have pointed out in the annexedclaim certain novel features of the invention, it will be understoodthat various omissions, substitutions and changes in the forms anddetails of the device illustrated and in its use and operation may bemade by those skilled in the art without departing from the broad spiritand scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:-

A gaseous electric discharge device comprising a tubular container,electrodes sealedthereln at the ends thereof, a gaseous atmospheretherein at a pressure greater than 2 mm. at room temperature and avaporizable material therein, one of said electrodes being an auxiliaryelectrode and two of said electrodes being main discharge supportingelectrodes, said auxiliary electrode being mounted adjacent one of saidmain discharge supporting electrodes and being interposed between saidmain electrode and the adjacent end of the container, the distancebetween said main electrode and said auxiliary electrode being greaterthan the diameter of said container, said auxiliary electrode beingconnected through a resistance to the main electrode other than that towhich said auxiliary electrode is adjacent.

EDUARD G. DORGELO.

